The overall goal of the proposed research is to continue the investigation of hearing in complex environments in awake, behaving cats. Many aspects of the precedence effect have been extensively measured using psychophysical experiments in humans. Less prevalent are the behavioral and physiological experiments in animals. Even less common are the experiments where behavior and physiology are measured simultaneously in each subject. These simultaneous behavioral and physiological experiments in awake behaving cats are important because they tell us on a trial-by-trial basis exactly where the animals identify a presented sound source and the underlying neural correlates to that source's identified location. It is already known that cats experience the precedence effect and that single units in the inferior colliculus of anesthetized cats show correlates to localization dominance and echo thresholds, but much is still unknown about many of the aspects of the precedence effect including the buildup and breakdown of echo suppression and the Franssen Effect. The objective of the proposed training is to investigate the influence of echoes on sound localization while combining the psychophysical and neurophysiological approaches in cats. [unreadable] [unreadable]